The invention relates generally to the field of broadcast technologies, and more particularly to novel techniques for utilizing available spectrum and bandwidth to improve features offered to audiences.
Conventional “over the air”, terrestrial broadcasting technologies have existed for many years, and have been improved and refined to their present state by successive waves of innovation. In general, utilizing agreed-upon broadcast protocols, transmitters send encoded data that may be repeated, amplified, and eventually sent over dedicated portions of the electromagnetic spectrum to receivers. The receivers, typically televisions and so-called “set top boxes” receive and decode the data for viewing, listing, recording, and so forth. Such technologies have been supplemented by cable transmissions, satellite transmissions, Internet transmissions, and so forth. Broadcast media still, however, holds a very important place in the range of options available for entertainment and information dissemination.
One disadvantage in current terrestrial broadcast technologies is the inability to offer more sophisticated paradigms for entertainment and information due to the lack of return channels. In certain new technologies, such return channels allow for the receiver to communicate with the transmitter, allowing for highly interactive experiences. These return channels are common for Internet communications, of course, owing to the 2-way nature of Internet communications. However, terrestrial broadcast is a fixed, 6 MHz one-way digital broadcast technology. Heretofore, new digital communication technologies, such as so-called “cognitive radio”, cannot be used in current broadcast because of the lack of return channel from the receiver to the transmitter. Moreover, the use of spectrum for terrestrial video broadcast services such as television is not as efficient as it can be. As the need for radio spectrum rises greatly, the need for more efficient technology is needed.
Another drawback in traditional terrestrial broadcast stems from the natural limits of available spectrum. Traditional communications devices rely upon building the “rules” for spectrum use into the design of receiving devices. For example, in the United States, television receivers are designed to receive 6 MHz wide signals, using the NTSC analog or ATSC 8-VSB modulation specified by the FCC, occupying frequencies designated to broadcasters by the FCC (i.e., channel number) in a specific channel within a specific band of the RF spectrum (i.e., VHF channels 2-13; UHF channels 14-51). Thus, television receivers can tune across the band and receive various station signals precisely located at predisignated channels, but they have little or no capability to adapt to changing spectrum use. While such hardware based receiver designs allow for very low cost receivers, the current level of receiver design overconstrains flexible use of spectrum.
On the other extreme, much early development work has been done on software defined radio and cognitive radio. In general, software based signal demodulation requires costly very-wideband analog to digital conversion and a large amount of expensive computational power. In many approaches, the spectrum is scanned and analyzed and appropriate demodulation code applied to receive a particular signal. This necessitates frequent rescans. As any consumer who starts a television “setup scan” knows, this is a time consuming process and it is not conducive to responsive channel changes.